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and 2 parts by weight of sulphuric acid of D — 1-845) are poured and on
to this are carefully dropped 20 grams of the glycerine, the beaker being
externally cooled with water meanwhile. The product is subsequently
transferred, with every precaution, to a graduated cylinder and note taken
if the nitroglycerine separates promptly and if it is pale and clear. When
the separation >of the nitroglycerine from the acid liquid is sharp, the volume
•of the former is measured ; multiplication of this volume by 1-609 (specific
gravity of nitroglycerine at 15°) gives the weight.
Glycerine liquors obtained directly by saponification with alkali or in an
autoclave contain 5-10% of glycerine, whereas those resulting from saponifica-
tion by Twitchell's method or by enzymes contain 12-19%.
Crude glycerine (concentrated) usually contains 80-90% of glycerine and
varying quantities of salts (ash), residue fixed at 160°, free acids or alkalies, etc.
Refined glycerine (pure, puriss.) should be free or almost so from the different
impurities already mentioned (see Pure Glycerine, -2).
Double distilled glycerine for pharmaceutical purposes should, in particular,
satisfy the various tests indicated under 2.
Dynamite glycerine should have a specific gravity not less than 1-26.1, should
be perfectly neutral, should contain no more than traces of chlorides (not more
than 0-025% °f NaCl), sulphates, lime, magnesia, alumina and reducing sub-
stances, and not more than 0-25% of residue fixed at 160°. In the nitration
test it should give not less than 200 % of nitroglycerine (theoretical yield, 246-7%),
which should separate promptly as a colourless or almost colourless, perfectly
clear liquid.resence of glucose. The presence of the latter may be